Abstract

Background

Electroacupuncture (EA) is currently one of the most popular acupuncture modalities.
However, the continuous stimulation characteristic of EA treatment presents challenges
to the use of conventional functional Magnetic Resonance Imaging (fMRI) approaches
for the investigation of neural mechanisms mediating treatment response because of
the requirement for brief and intermittent stimuli in event related or block designed
task paradigms. A relatively new analysis method, functional connectivity fMRI (fcMRI),
has great potential for studying continuous treatment modalities such as EA. In a
previous study, we found that, compared with sham acupuncture, EA can significantly
reduce Periaqueductal Gray (PAG) activity when subsequently evoked by experimental
pain. Given the PAG's important role in mediating acupuncture analgesia, in this study
we investigated functional connectivity with the area of the PAG we previously identified
and how that connectivity was affected by genuine and sham EA.

Results

Forty-eight subjects, who were randomly assigned to receive either genuine or sham
EA paired with either a high or low expectancy manipulation, completed the study.
Direct comparison of each treatment mode's functional connectivity revealed: significantly
greater connectivity between the PAG, left posterior cingulate cortex (PCC), and precuneus
for the contrast of genuine minus sham; significantly greater connectivity between
the PAG and right anterior insula for the contrast of sham minus genuine; no significant
differences in connectivity between different contrasts of the two expectancy levels.

Conclusions

Our findings indicate the intrinsic functional connectivity changes among key brain
regions in the pain matrix and default mode network during genuine EA compared with
sham EA. We speculate that continuous genuine EA stimulation can modify the coupling
of spontaneous activity in brain regions that play a role in modulating pain perception.